1. Field of Invention
The present invention relates to a method of feeding one unitary sheet of a trim cover assembly used on an automotive seat to a multiple-needle sewing machine for the purpose of forming plural decorative stitches on the trim cover assembly.
2. Description of Prior Art
In fabrication of an automotive trim cover assembly, there has been practiced a multiple stitching process which uses a multiple-needle sewing machine (or a multi-axis sewing machine) having a plurality of sewing needles mounted thereon, so as to form plural decorative stitched seams upon the trim cover assembly at one time.
FIGS. 1A and 1B shows an example of conventional multiple stitching method, in which it is seen that a trim cover assembly (1) is fed to a multiple-needle sewing machine (M) and then formed with a plurality of stitched seams (41, 42, . . . ) extending linearly in parallel with one another. (See the Japanese Laid-Open Patent Pub. No. 64-34394, for instance).
Briefly stated, the trim cover assembly (1) comprises a typical three-layer lamination of a top surface layer (111), a wadding layer (112) of urethane foam slab material and a wadding cover (113), and the sewing machine (M) is provided with a plurality of needles (M1, M2, . . . M10). As shown in FIG. 1B, the decorative seams (41, 42, . . . ) are formed in the trim cover assembly (1) in a parallel spaced-apart relation with one another, by means of those needles.
This parallel rectiliner multiple sewing, however, is defective in having difficulty in effecting a slant sewing for forming an obliquely stitched point on the cover member, as may be required from a design demand, in which case, it is necessary to prepare a separate slant section of the trim cover assembly and sew the same to the main body of the trim cover assembly.
Further, the present sewing method is not applicable to such new mode of rear seat as shown in FIG. 2(D), which has a protruded portion (H) formed centrally thereof. As illustrated, the protruded portion (H) varies in height from the forward side to the rearward side; namely, its height increases as it proceeds from the forward side of seat to the rearward side of same. The trim cover assembly covering this kind of seat requires a proper design and stitching in its seating surface section in order to give parallel stitched seams thereon. Thus, in this case, can the above-mentioned sewing method be directly applied, and separate stitched sections must be sewn together to form a required portion of trim cover assembly that covers the protruded portion (H) in question.
This problem is of a particular concern, and will be described more concretely with reference to FIGS. 2(A) to 2(E). As understandable from FIGS. 2(A), 2(C) and 2(D), the seat cushion (SC) of a rear seat is composed of a urethane foam molded cushion body (2), with the trim cover assembly (1) fixed thereover by means of the stitch sewing. FIGS. 2(A) and 2(C) show in cross-section the forward and rearward sides of seat cushion (SC), respectively along the lines A--A and C--C in FIG. 2(D), thus depicting a small height of the protruded portion (H) at the rearward side as in FIG. 2(A) and a greater height of same at the forward side as in FIG. 2(C). With such seat cushion structure, a technical concern is directed to how the stitches or stitched seams are to be formed neatly in parallel, while conforming to the uneven shape of the protruded portion (H). This can be achieved from the stitching pattern represented in FIG. 2(E), which schematically shows an exploded state of the trim cover assembly (1). As shown, excepting the central set of stitches (41, 41), the remaining stitches (42, 43) must be drawn by a separate sewing step which involves orienting the trim cover assembly (1) at a required angle. It follows thus that, during the sewing upon the cushion body (2), the unitary sheet of trim cover assembly (1) should be subject to a parallel stitching for forming the pair of central stitches (41, 14) and also to a non-parallel stitching for forming, relative thereto, a plurality of slant stitches (42, in a symmetrical fashion.
Consequently, this factor is practically an obstacle against the availability of the above-mentioned automatic plural stitching method using a multiple-needle sewing machine.